1. Field of the Invention
The present invention relates to packet priority control.
2. Description of the Related Art
With the rapid expansion of the Internet, there have been more cases of business done by using the Internet to transmit and receive packets between a client and a server, such as electronic commerce. A packet transmitted by the client is delivered to the server via a router or the like. In this case, when the network is congested, the router discards the packet so as to avoid the congestion. In mail-order selling of products and the like, however, there are packets that are desired to be delivered to the server and the client without fail, such as a packet for ordering a product and a packet for confirming the order. Such packets need priority control, in which the packets are transferred before other packets.
As a priority control technique of the client and the server, there is a method of transmitting a transmission packet with a value indicating priority included in a TOS field (layer 3) of the packet. TOS is a field related to priority transfer control included in an IP packet header specified by the Internet Protocol (RFC 791). Priority control techniques of the router include: (i) a technique of making priority transfer on the basis of the priority in the TOS field; (ii) a technique of making priority transfer by determining a priority on the basis of a static or dynamic policy of the router itself; and (iii) a technique of making priority transfer by determining a priority on the basis of the static or dynamic policy of the router itself and then rewriting the TOS field value of the packet to be transferred.
With the conventional priority control techniques, however, it is difficult for the user of the server or the client to make the setting in the TOS field of an IP packet at an application level, and therefore it is in effect difficult for the user of the server or the client to set a priority. Thus, the user of the server or the client cannot specify a packet desired to be given priority for priority control. Thus, since even when the router can make priority transfer on the basis of the TOS value, it is difficult to set the TOS value at the application level, it is not possible to make priority transfer of a packet desired by the user of the client or the server.